B08_Attachment_4_BAND_MOD7_Exceptions_Report_Signed.pdf

This is a Technical Memorandum documenting culvert design exceptions for the Bandelier National Monument Underground Utilities Rehabilitation project (BAND 266697) managed by Jacobs Engineering Group, Inc. for the National Park Service Denver Service Center.

The project addresses repairs to an existing corrugated metal pipe (CMP) culvert beneath Route 0010 Entrance Road at Bandelier National Monument. The culvert inlet, buried over 6 feet below ground level near the Visitors Center, features historic stone headwalls that the National Park Service required be preserved in place. The design involves uncovering the silted culvert invert, restoring the existing historic stone headwall, and regrading a roadside ditch to direct flows to the culvert inlet. The road is classified as a Class I Principal Park Road with a posted speed limit of 25 mph and current average daily traffic of approximately 250 vehicles. The design exception pertains to the clear zone requirement, which specifies 6 feet per AASHTO Guidelines for Geometric Design of Low-Volume Roads 2019 but is designed at 3 feet due to the historic headwall preservation constraint. Risk analysis indicates low risk given lower vehicle speeds, low traffic volumes, and no historical accident records. Mitigation features include installation of a drop inlet with flatter design slopes, reduced speed limit signs, guardrail, curb, and edge stripe. The exception and associated risk mitigation were reviewed and formally approved by the National Park Service on March 9, 2026, with recommendations from Jacobs project personnel and NPS management.